354 



To explain this he invoked the aid of chemistry, and the well- 

 known action of hot water containing alkalies in solution in soften- 

 ing and decomposing silicates, extracting some ingredients and 

 combining others, the form of the rock remaining unchanged. 



Prof Hitchcock exhibited some very distinct specimens of grap- 

 tolite, a coralline fossil, from the rocks of Vermont. 



Dr. C. T. Jackson expressed the same opinion as on a former 

 occasion, that the pebbles found at Newport and in this State, as 

 at Roxbury, were formed mechanically by being rolled upon 

 beaches by the surf ; even the distortions and indentations might 

 be accounted for in this way, their parallels being now in process 

 of formation on the beaches of this State and of Maine. But in 

 regard to these Vermont pebbles, he believed that they might have 

 been formed from the rock, but not the rock from the pebbles as 

 Prof. Hitchcock maintains. In support of this view, he referred 

 to the experiments of M. Daubree, showing how siHcates become 

 soluble under moderately hot water in presence of alkalies, the 

 quartz being separated and crystallized. In contrast with the 

 immense denudation which has taken place in the North, he men- 

 tioned that in some places at the South, as at Dahlonega, Ga., the 

 rocks are so decomposed and soft as to allow of being shovelled to 

 a depth of 80 to 100 feet, none of the surface having been sub- 

 jected to drift or denuding agencies. 



Dr. A. A. Hayes, in reference to the mineral from Lake 

 Superior containing boracic acid, mentioned at the first 

 September meeting, observed that it presented two points 

 of special interest : one is that, though very compact, it 

 shows the composition of datholite better than the crys- 

 talline form of this substance ; the other is its econom- 

 ical value ; as it contains 22^ per cent, of boracic acid, if 

 abundant, it might be collected with commercial advan- 

 tage. 



In reply to a question of Mr, Kidder in relation to the 

 animals which eat the piles in Boston Harbor, Dr. A. A. 

 Gould replied that, though popularly called worms, they 

 are minute crustaceans, the Limnoria terebrans; they 

 are about /o of an inch long. 



